Small molecular weight compounds (1000-2000 dalton) found in bovine lenses coprecipitate with alpha and beta crystallins at pH 5.1. This complex possesses crystalline organization as viewed by X-rays, which is absent when the small molecular weight compounds are removed by dialysis. Among these small molecular weight compounds phosphopeptides are responsible for the crystalline organization (Exp. Eye Res., 14, 251 and 259 (1972); 25, 613 (1977). The phosphopeptides themselves are heterogeneous mixtures but four amino acids; glutamic acid, aspartic acid, serine and glycine accounts for 50% of the composition. The purpose of the present investigation is to isolate and characterize the major phosphopeptides present in bovine lenses. Both analytical and synthetic approach will be used. Each isolated and synthesized phosphopeptide will be tested regarding the capacity to organize alpha and beta crystalline into a crystalline matrix. The study will attempt to answer whether 0- or N or both phosphates are necessary to perform this function; what is the minimum length and amino acid sequence of phosphopeptides that are required for ability to organize macromolecules into a crystalline lattice. Furthermore the nature of interaction will be studies by ligand binding techniques.